Summary

1. Adult brown trout (Salmo trutta L.) of both sea-run (sea trout) and fresh-water stream (brown trout) forms were captured in the vicinity of Aberdeen and acclimatized to full-strength sea water for periods of up to 5 months.

3. The patterns of regulation of these concentrations are very nearly the same in both forms. Brown trout and sea trout, at least in eastern Scotland, thus appear to be virtually identical in osmotic and ionic regulatory abilities. However, there is a possibility that there is a difference between the two forms with respect to mechanisms controlling blood acid-base balance.

4. The patterns of regulation shown by Scottish fish are the same as those shown by American hatchery fish treated similarly. The different populations of the species seem not to have diverged significantly from one another in this regard after many generations of more or less complete genetic isolation.

5. The species Salmo trutta is strongly homoiosmotic. Internal concentrations are either unchanged or increase by less than 10% above fresh-water levels with long-term acclimatizations to half and full sea water. The brown trout is the first salmonid species known to regulate so well.

Contribution number 927 from the Woods Hole Occanographic Institution.

Similar articles

Other journals from The Company of Biologists

Many organizations that use sonar for underwater exploration gradually increase the volume of the noise to avoid startling whales and dolphins, but a new Research Article from Paul Wensveen and colleagues reveals that some humpback whales do not take advantage of the gradual warning to steer clear.

Many animals stabilize their vision by swivelling their eyes to prevent the image from smearing as they move. A new Research Article on tadpoles from Céline Gravot and colleagues shows that contrast between objects in their view affects the strength of this visual reflex, suggesting that the eye may be processing the image at a basic level to produce the reflex.

When starting her own lab at James Cook University, Australia, Jodie Rummer applied for a Travelling Fellowship from JEB to gather data on oxygen consumption rates of coral reef fishes at the Northern Great Barrier Reef. A few years later, Björn Illing, from the Institute for Hydrobiology and Fisheries Science, Germany, followed in Jodie’s footsteps and used a JEB Travelling Fellowship to visit Jodie’s lab. There, he studied the effects of temperature on the survival of larval cinnamon clownfish. Jodie and Björn’s collaboration was so successful that they have written a collaborative paper, and Björn has now returned to continue his research as a post-doc in Jodie’s Lab. Read their story here.

Where could your research take you? The deadline to apply for the current round of Travelling Fellowships is 30 Nov 2017. Apply now!